Sense of agency (SoA) refers to the feeling of controlling one’s own actions, and the experience of controlling external events with one’s actions. The present study examined the effect of strength of intentional effort on SoA. We manipulated the strength of intentional effort using three types of buttons that differed in the amount of force required to depress them. We used a self-attribution task as an explicit measure of SoA. The results indicate that strength of intentional effort enhanced self-attribution when action-effect congruency was unreliable. We concluded that intentional effort importantly affects the integration of multiple cues affecting explicit judgments of agency when the causal relationship action and effect was unreliable.

Humans are capable of associating actions with their respective consequences if there is reliable contingency between them. The present study examined the link between the reliability of action consequence and the readiness potential (RP), which is a negative potential observed from about 1–2 s prior to the onset of an action with electroencephalography. In a condition of constant outcome, the participants’ voluntary action always triggered beep sounds; thus, they were able to perceive the contingency between their action and the sound. In contrast, in a condition of inconstant outcome, the participants’ actions only triggered the sound in half the trials. We found that both the early and late RPs were larger in the condition of constant compared to the condition of inconstant outcome. Our results showed that the RPs preceding the voluntary action reflected the reliability of action consequence. In other words, the action-effect contingency enhanced neural activities prior to the action.

Sense of Agency (SoA) refers to the experience of controlling external events. SoA is considered to have predictive and postdictive aspect. Recent studies have investigated the relationship between SoA and event-related potentials, but these studies focused only on the postdictive aspect, while the brain activities related to the predictive aspect of SoA remain unclear. In the present study, we focused on readiness potential (RP) and examined the influence of prediction of SoA on RP. In the experiment, participants pressed a key to trigger a tone, and the event-related potentials before and after the key-press was recorded. In the normal predictive condition, all the tones were presented after key-press, thus participants could predict that their key-press would probably cause a tone. In contrast, in the low predictive condition, one third of the tones were presented before the key-presses, thus the causability of key-presses on tones were doubtful. The results indicated earlier RP in the normal predictive condition relative to the low predictive condition, although the difference did not reach significant level due to the small sample size. We will increase participants to confirm the difference in RP between the two predictive conditions in future work. We believe that our work provides important knowledge for the understanding of the neural basis of SoA.

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